The toxin-antitoxin system of Staphylococcus aureus.

TA系统在细菌中很常见。TA系统有8个家族，它们都在相似的原理下运行，都有稳定的毒素和不稳定的抗毒素，这些毒素容易在应激时诱导蛋白酶。在TA对中，MazEF和RelBE系统被研究得最好。基因组分析显示，在许多革兰氏阳性细菌中存在MazEF和RelBE类似基因。初步研究表明，金黄色葡萄球菌中的MazF毒素是一种特异的内切核糖核酸酶，它切割在V或V‘可以是A、C或G的VUUV’位点。我们推测，用合成的小分子化合物破坏毒素与抗毒素迷宫的结合来释放MazF的毒性是可行的，从而为开发新型抗菌化合物提供了一条新的途径。我们还检测了MazF对mRNA切割的特异性，发现一些管家和毒力调节因子mRNAs是不受影响的，而其他一些mRNAs，如Hla、SpA和SIGB则很容易被切割。我们怀疑RNA结合蛋白可能保护其中的一些mRNAs。由于我们已经从我们的中试筛选中获得了一些“假定的化合物”，我们建议在实验中使用一种新型的荧光DNA-RNA杂化底物来筛选抗迷宫的小分子合成化合物。为了实现上述目标，我们开展了以下工作：(1)鉴定保护选择性基因(如选择性看家基因和SARA)免受MazFsa切割的核糖核酸结合蛋白(S)；(2)建立一种筛选干扰MazEsa功能或与MazFsa结合的小分子(S)的方法。总而言之，这些数据将突出革兰氏+细菌TA系统的独特性。由于针对多重耐药金黄色葡萄球菌的治疗选择有限，我们的筛选试验将为开发针对金黄色葡萄球菌的新型抗菌疗法提供初步的化合物。

TA systems are common in bacteria. There are eight families of TA systems all of which operate under a similar principle, with a stable toxin and a labile antitoxin prone to proteases that are induced upon stress. Among the TA pair, the MazEF and RelBE systems are the best studied. Genomic analysis revealed MazEF and RelBE paralogs in many Gram+ bacteria. Preliminary studies indicated that the MazF toxin in S. aureus is a specific endoribonuclease that cuts at a VUUV’ site where V or V’ can be A, C or G. We speculate that it may be feasible to disrupt the binding of the toxin to the antitoxin MazE with small synthetic compounds to unleash the toxicity of MazF, thus representing a new approach for the development of novel antimicrobial compounds. We also examined the specificity of MazF on Mrna cleavage and found that some housekeeping and virulence regulator mRNAs are spared while others such as hla, spa and sigB are easily cleaved. We suspect RNA-binding protein may protect some of these mRNAs. As we already have a few “putative compounds” from our pilot screen, we propose to screen for small synthetic compounds against anti-MazE, using a novel fluorescent DNA-RNA hybrid substrate in the assay. To satisfy the above goal, we have developed the following aims: I) Identification of RNA binding protein(s) that protects selective mRNA (e.g. selective housekeeping gene and sarA) from MazFsa cleavage; II) developing an assay to screen for small molecule(s) that interferes with function or binding of MazEsa to MazFsa. Collectively, these data will highlight the uniqueness of the TA systems in Gram+ bacteria. As therapy options against multidrug resistant S. aureus are limited, our screening assays will provide the initial compounds against MazE for the development of novel antimicrobial therapy against S. aureus